Similar in structure and evolutionary origin but having different functions, as a human's arm and a seal's flipper.

Being one of a pair of chromosomes, one from the female parent and one from the male parent, that have genes for the same traits in the same positions. Genes on homologous chromosomes may not have the same form, however. For example, one chromosome in a pair of homologous chromosomes may contain a gene for brown eyes, and the other a gene for blue eyes. Human females have 23 pairs of homologous chromosomes (including the two X chromosomes), while human males have 22 because the Y chromosome is not paired.

Belonging to or being a series of organic compounds, each successive member of which differs from the preceding member by a constant increment, especially by an added CH2 group. The alkanes (methane, ethane, propane, and others) are a homologous series of compounds.